Pick off means for an electrostatic reproduction device

ABSTRACT

An electrophotographic apparatus of the type having a photoconductor section supported around a portion of an imaging drum periphery is provided with a recess adjacent the leading edge of the photoconductive section. Copy sheets are fed into transfer contact with the section with a leading portion extending over the recess and a deflector is moved into and out of the recess to pick off the copy sheet. Alternative separating structure is provided to urge the copy sheet away from the pickoff member to avoid damage to the copy sheet image.

United States Patent Hodges, deceased 1451 Mar. 14, 1912 [54] PICK OFF MEANS FOR AN ELECTROSTATIC REPRODUCTION DEVICE [72] Inventor: Howard T. Hodges, deceased, late of Perinton, NY. by Claire F. Hodges, executrix [73] Assignee: Eastman Kodak Company, Rochester,

[22] Filed: Sept. 26, 1969 21 Appl. No.: 861,508

[52] US. Cl ..355/l1, 355/3 [51] Int. Cl. ..G03g 15/00 [58] Field ofSearch ..355/3, 8, 11,12, l4, 16;

[56] References Cited UNITED STATES PATENTS 2,889,758 6/1959 Bolton ..l17/17.5X

3,062,108 Mayo ..355/8 3,109,355 11/1963 Ritzerfeld 355/11 X 3,504,969 4/1970 Martel ..35S/l6 3,506,259 4/1970 Caldwell et al. ..355/3 X 3,508,824 1/1970 Leinbach et al. ..355/3 Primary Examiner-John M. Horan Assistant ExarJninerThomas A. Mauro Attorney-Robert W. Hampton and Gary D. Fields [57] ABSTRACT An elect'rophotographic apparatus of the type having a photoconductor section supported around a portion of an imaging drum periphery is provided with a recess adjacent the leading edge of the photoconductive section. Copy sheets are fed into transfer contact with the section with a leading portion extending over the recess and a deflector is moved into and out of 'the recess to pick off the copy sheet. Alternative separating structure is provided to urge the copy sheet away from the pickoff member to avoid damage to the copy sheet 1mage.

6 Claims, 6 Drawing Figures Patented March 14, 1972 5 Sheets-Sheet 1 HOWARD T HODGES,DECEASED, BY CLAIRE F. HODGES,EXECUTRIX INVENTOI BY WMK/M ATTORNEYS Patented March 14, 1972 3,649,115

5 Sheets-Sheet 2 HOWARD T. HODGESDECEASED,

BY CLAIRE F. HODGES,EXECUTR!X mvzumn mun/M ATTORNEYS Patented "March 14, 1972 3,649,115

' 5 Sheets-Sheet 5.

F/G.5 F7515 HOWARD T. HODGES, DECEASED,

BY CLAIRE F. HODGES,EXECUTRIX INVENTOII WMA/M ATTORNEYS PICK OFF MEANS FOR AN ELECTROSTATIC REPRODUCTION DEVICE CROSS-REFERENCE BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to electrophotography and, more particularly, this invention relates to an improved electrophotographic copier wherein means are provided to facilitate separation of a copy sheet from an electrophotosensitive element subsequent to toner transfer.

2. Description of the Prior Art Copy making by the electrophotographic process is well known. Illustratively, one form of electrophotography comprises the following basic steps: (a) uniformly electrostatically charging the photoconductive surface of an electrophotosensitive element; (b) imagewise exposing the photoconductive surface to a light pattern, thereby selectively dissipating. the uniform charge to form an electrostatic image of the original copy thereon; (c) applying toner to the photoconductive surface to form a toner image defined by the electrostatic image; (d) transferring the toner image from the photoconductive surface to a copy sheet; and (e) permanently fixing the toner image to the copy sheet.

In many electrophotographic machines designed for carrying out the process set forth above, it is common for the electrophotosensitive element to have a cylindrical or otherwise closed-loop configuration, the electrophotosensitive element may be repetitively cycled through the electrophotographic copying process, each time transferring to a copy sheet the toner image formed on the photoconductive surface thereof. The toner image transfer step is usually accomplished by advancing the copy sheet and the toner-bearing surface of the electrophotosensitive element, in contiguous relationship, past a transfer station which comprises means for electrostatically charging the copy sheet to a polarity to attract the toner image thereto. By this arrangement the toner image is stripped from the photoconductive surface and deposited on the copy sheet in substantially the same pattern as it existed on the photoconductive surface. Subsequent to the toner transfer step it is necessary to separate the copy sheet from the photoconductive surface in order for the copy sheet to progress past a fusing station where the transferred toner may be permanently affixed to the copy sheets so as to form a hard copy."

In machines employing a closed-loop electrophotosensitive element, particularly one employing a cylindrically shaped element, it has been common to experience difficulty in separating the copy sheet from the photoconductive surface subsequent to toner transfer. Such difficulty is commonly attributed to a combination of two factors. First, as indicated above, the copy sheet acquires an electrostatic charge during the transfer step which results in an affinity between the copy sheet and the toner carried by the photoconductive surface. Such affinity causes the copy sheet to adhere to the tonerbearing photoconductive surface and follow it as it is recycled through the electrophotographic copying process. Secondly, because of the closedloop configuration of the electrophotosensitive element, neither a leading nor a trailing edge of the element is provided whereby a separation of the two surfaces might be facilitated.

Heretofore, in electrophotographic copying machines of the type described above, it has been common to employ rather complex mechanisms for stripping the copy sheet from the electrophotosensitive element subsequent to the toner image transfer process. Use of simple mechanical devices has been avoided because of the possibility of damaging the relatively delicate and costly photoconductive surface of the electrophotosensitive element. To avoid contact with such surface it has been common to employ charged members, spac,ed.-from the photoconductive surface, which are electrostatically. at.- tractive to the copy sheet and thus cause the copy sheet to move thereto. Alternatively, and. often, in combination with the charged members, vacuum and. air puff devices. have been employed to suck or blow the leading edge of the, copy sheet away from the direction of travel of the electrophotosensitive element. Notwithstanding the sophistication of.- such separation apparatus, separation failure is occasionally experienced, such failure usually necessitating machine shutdown.

SUMMARY OF THE INVENTION.

In accordance with the present invention, apparatus is pro,- vided for overcoming the aforementioned separation difficulty of the prior art. According to a preferred embodiment of the invention, the conventional closed-loop configuration of the electrophotosensitive element is replaced by-a noncontinuous arcuately shaped element having leading and trailing edges, and means are provided for laying down a copy sheet on the photoconductive surface of the element insuch a manner that the leading edge of the copy sheet extends forwardof the leading edge of the electrophotosensitive element, thereby providing a readily engageable flap which may be engaged by a simple mechanical pickoff member and guided away from the direction of travel of the electrophotosensitive element. Means are also provided for synchronizing the action of the mechanical pickoff member with the passage of the leading edge of the copy sheet therepast, thereby assuring that the mechanical member contacts only the copy sheet, leaving the delicate photoconductive surface untouched.

Further advantages of the invention will become apparent from the description which follows, taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partial diagrammatic side elevation of a preferred automatic electrophotographic copier of the invention;

FIG. 2 is a fragmentary front elevation, takenalong. line 2- 2 of FIG. 1, showing a copy sheet advancing and pickoff mechanism with portions omitted for clarity of illustration; and

FIG. 3 is a fragmentary, diagrammatic, side. elevation of an alternative pickoff means for deflecting the copy sheet away from the electrophotosensitive element, which. includes a vacuum roller;

FIG. 4 is a fragmentary, diagrammatic, side elevation of a further alternative pickoff means utilizing a corona discharge device;

FIG. 5 is a fragmentary, diagrammatic, side elevation of a still further alternative pickoff means utilizing a mohair brush; and

FIG. 6 is a fragmentary, diagrammatic, side elevation of a still further alternative pickoff means utilizing an air emission source.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In accordance with this invention, an automatic electrophotographic copying machine is shown in FIG. I for making a hard copy of the pattern la formed on the original copy 1. Generally, the machine includes the following elements: a noncontinuous and arcuately shaped electrophotosensitive element 10; drive means 20 for advancing element 10 in a substantially circular path whereby element 10 is continuously recycled through the electrophotographic copying process; a charging station 25 whereby the surface of element 10 may be uniformly electrostatically charged; an exposure station 30 where an image of light pattern Ia may be focused on the surface of element 10 so as to selectively dissipate the charge thereon, leaving behind an electrostatic image corresponding to light pattern Ia; a developing station 35 whereby the electrostatic image so formed is made visible with toner particles;

a transfer station 40 whereby the toner image formed on element 10 may be transferred to the surface of a copy sheet 55; a copy sheet advancing mechanism 90 for advancing copy sheet 55 from a stack 56 of such sheets to transfer station 40 in timed-relationship with the arrival of element 10 thereat; pickoff means 75 for engaging the leading edge 55a of copy sheet 55 and guiding it away from the direction of travel of element 10; and fusing station 45 for permanently fixing the transferred toner image on the copy sheet 55. The machine also includes a projection station which serves to illuminate original 1 and project the image thereof on element as the latter passes exposure station 30. and means for advancing original 1 into the projection station at the same linear rate as that at which element 10 is advanced by drive means and in synchronism with the passage of element 10 past exposure station 30. Optionally the machine includes a cleaning station 50 which merely serves to remove nontransferred toner particles from the surface ofelement 10.

Electrophotosensitive element 10 is preferably comprised of an arcuate transparent support plate 11 (e.g., ordinary glass or clear plastic) having a multilayer web 12 stretched across the entire longitudinal dimension thereof. Secured to the leading edge 11a and trailing edge 11b of plate 11 is a pair of resilient pads 16 which prevent a sharp bending of web 12 as it is stretched over these edges. Web 12 is preferably comprised of a transparent conductive layer 13 having disposed thereon a photoconductive insulating layer 14. It is, of course, the outer surface of the photoconductive insulating layer 14 which is electrostatically charged, imagewise exposed and developed during the copying process. By selecting transparent materials for plate 11 and the conductive layer 13 of web 12, it is possible to expose the photoconductive layer 14 through the base (i.e., from the concave side of element 10) and eliminate the necessity of cleaning station 50 which serves merely to remove nontransferred toner from the photoconductive surface of element 10 which would interfere with exposure from the opposite side. Suitable transparent conductive materials are disclosed in U.S. Pat. No. 3,245,833, to D. J. Trevoy. Suitable photoconductive materials and processes for their manufacture are disclosed in U.S. Pat. No. 3,l4l,770, to D. R. Davis et al.

Arcuate support plate 11, is laterally supported along the edges thereof by a pair of circular spaced rims 60 and 61, as in FIG. 2. Each rim is rigidly mounted on a rotatable drive shaft 21, as by a plurality of spoke members (not shown). Shaft 21 is driven by drive means 20, such as an electric motor. Suspended from rims 60 and 61 adjacent the trailing edge 11b of plate 11, and extending toward shaft 21, is a pair of spaced support members 63 and 64 between which is rotatably mounted a supply reel 65, whereon a fresh multilayer web 12 may be wound. Also suspended from rims 60 and 61 adjacent the leading edge 11a of plate 11, and extending toward shaft 21, is a second pair of spaced support members 67 between which is rotatably mounted a takeup reel 68 whereon web 12 may be wound whenever replacement of the web is deemed desirable. Suitable apparatus is provided for advancing web 12 from the supply reel 65, along the surface of plate 11, to takeup reel 68. Such web advancing apparatus is more fully described in the copending, commonly assigned application, U.S. Ser. No. 777,717 to Howard T. Hodges, filed Nov. 21, 1968, now abandoned.

Projection station 5 is comprised of platens 6, 60; light sources 7, 7a; a 45 reflector or mirror 8; and a lens system 9. Platen 6 is transparent so as to permit light pattern 1a to be illuminated by light sources 7, 7a. Reflector 8 and lens system 9 serve to form an image of pattern 1a on the photoconductive layer 14 of element 10 as the latter passes exposure station 30. The amount of exposure at station 30 is controllable by varying the rate at which element 10 advanced or by varying the intensity of light sources 7, 7a or by varying the aperture of lens system 9 or a combination of these.

In order to advance original copy 1 through projection station 5, between the platens 6, 6a, two pairs of nip rollers 3, 3a

and 4, 4a are provided. Synchronization of the rate at which the original copy 1 is advanced through projection station 5 with the rate at which element 10 passes exposure station 30 is accomplished by a timing belt 2 which is arranged to ride in a I groove 60a formed on the periphery of rim 60 (shown in FIG. 2) and over rotatable shafts upon which nip roller 3 and 4 are mounted.

The copy sheet or receiver advancing mechanism includes a cam 91, disc 95, drive belt 93, nip roller 100, 101 and friction wheel 105. Cam 91, mounted for rotation with drive shaft 21, is substantially sector-shaped, having two plane surfaces 91a and 91b extending radially from drive shaft 21 and an arcuate surface 91c connecting the outer terminators of the plane surfaces 910 and b.

Disc 95 is secured to a shaft 96 which, in turn, is mounted for rotation on the free end of a lever 97. The opposite end of lever 97 is pivotally mounted to the machine housing by pin 98. Spring means 99 is provided for biasing the free end of lever 97 in a counterclockwise direction and stop means (not shown) is provided for positioning lever 97 so that the periphery of disc 95 will engage the arcuate surface 91c of cam 91 and be rotated thereby, due to frictional engagement, as the cam 91 rotates with drive shaft 21.

Secured to rotatably mounted shaft 96, adjacent disc 95, is a pulley 94 which, through drive belt 93, serves to impart a rotational movement in nip rollers 100, 101 when the pulley 94 is caused to rotate by cam 91. Nip rollers 100, 101 are preferably made of hard rubber and are mounted on rotatable shafts 102 and 103, respectively. The shafts are arranged such as to establish a contiguous relationship between the peripheries of the rollers. Mounted for rotation with shaft 102 is a pulley 104 which is driven by belt 93.

A friction wheel 105, preferably comprised of a soft foam rubberlike material, is mounted on a rotatable shaft 106 which is vertically movable above the forward portion of copy sheet stack 56. Spring means (not shown) is provided for biasing shaft 106 in a downward direction so as to insure frictional engagement between the wheel 105 and the uppermost copy sheet of the stack. Drive means (not shown) is provided for producing a constant clockwise rotation of the friction wheel, as viewed in FIG. 1. Such drive means is preferably activated by drive source 20. An arcuate guide member 107 guides the leading edge 55a of sheet 55 into the nip of rollers and 101. Thus, even as element 10 is progressing through the initial stages of the copying process, the leading edge of copy sheet 55 is presented at the nip of rollers 100 and 101. The material from which wheel is constructed and the downward force exerted on shaft 106 by the spring means (not shown) should be such that the friction between wheel 105 and the upper surface of sheet 55 will be sufficiently low as to permit slipping when edge 55a reaches the rollers nip.

Thus, since the copy sheets leading edge is within the nip of rollers 100 and 101 when cam 91 engages disc 95, the copy sheet will be advanced as the nip rollers are caused to rotate by belt 93. Such advancement by the nip rollers will continue during the period cam surface 91c is in contact with disc 95. This period is sufficient to advance the forward portion of copy sheet 55 into transfer station 40, under corona filaments 41 which cause the forward portion to electrostatically adhere to or contact the photoconductive surface 14. In this manner the copy sheet is drawn through rollers 100 and 101 even after cam surface 910 loses contact with disc 95. Alternatively, the length of cam surface 910 could be such as to cause rollers 100 and 101 to advance the entire length of copy sheet 55 into transfer station 40. A pair of curved guide members 108 and 109 serve to guide copy sheet 55 from rollers 100 and 101 to the transfer station.

Cam 91 is so oriented on drive shaft 21 that contact between cam surface 91c and disc 95 is made before the leading edge of element 10 reaches transfer station 40. ln this manner, the leading edge 55a of copy sheet 55 is caused to arrive at transfer station 40 slightly prior to the arrival of the leading edge of photosensitive element 10. Thus, the leading portion of the copy sheet overlaps the leading edge of element 10, thereby creating a flap 55b. It is this flap which facilitates the separation of the copy sheet from element 10.

The copy sheet pickoff mechanism 75 comprises a rotatable shaft 76, having a pickoff finger 77 and actuating lever 78 coupled thereto. As shown in FIG. 2, one end of shaft 76 is journaled in the machine housing and the free-end thereof extends laterally outward to a point approximately midway between rims 60 and 61. Shaft 76 is parallel to drive shaft 21 and is arranged just outside the circular path transversed by the electrophotosensitive element 10. Both pickoff finger 77 and actuating lever 78 extend perpendicularly from the shaft 76, the former extending from the free end of the shaft and the latter extending from a pointjust outside rim 61 as best seen in FIG. 2. As viewed along the longitudinal axis of shaft 76, finger 77 and lever 78 are angularly separated (see FIG. 1). A spring 79 is provided for biasing shaft 76 for counterclockwise rotation, as viewed in FIG. 1, and a stop means (not shown) is provided so as to cause shaft 76 to have a rest position such that finger 77 and lever 78 extend in the manner shown in phantom in FIG. 1. When shaft 76 is in such rest position, lever 78 projects slightly within the circular path of element 10, adjacent the outer edge of rim 61, and finger 77 is radially exposed just outside the circular path, midway between rims 60 and 61. The outer edge of rim 61 is provided with a laterally extending pin 62 which is arranged in a manner as to momentarily engage actuating lever 78 as rim 61 rotates.

By the arrangement described above, pin 62 acts as a cam which imparts a clockwise rotational movement to shaft 76 during the period in which it is engaged with lever 78. Such clockwise rotation of shaft 76 will cause pickoff finger 77 to dip into the circular path of element 10. Pin 62 is positioned on rim 61 in such a manner that the dipping of pickoff finger 77 occurs just prior to the passage of the leading edge 55a of copy sheet 55 thereunder. The duration of the dipping movement of pickoff finger 77 is, of course, determined by the duration of the engagement between actuating lever 78 and pin 62, and the latter period is governed by the length of actuating lever 78. A continued rotation of element causes pin 62 and lever 78 to disengage, thereby permitting finger 77 to return to its rest position under its spring bias. As finger 77 returns to its rest position it peels copy sheet 55 away from element 10 and directs it to fusing station 45 which comprises, for instance, an infrared heater which serves to melt the toner particles 38 and thereby fuse them to the copy sheet. Element 10 is then recycled through the copying process while the copy sheet passes through fuser 45 to fix the image thereto.

In FIGS. 36 a variety of arrangements is shown for accepting the leading portion of copy sheet 55, as presented by pickoff mechanism 75, and guiding the copy sheet further into fusing station 45 without disturbing the unfused toner image carried on the copy sheets surface. In FIG. 3, a perforated roller 120 having a vacuum slit 121 contained therein is arranged as shown. The suction of the vacuum is directed so as to draw the copy sheet to roller 120 as it leaves the transfer station. Alternatively a grounded metal roller 130 could be used in place of the perforated roller 120 and a corona emission source 131 could be positioned as shown in FIG. 4 to cause the copy sheet 55 to be attracted to roller 130.

In FIGS. 5 and 6 a soft brush 135 (e.g., mohair) and an air emission source 136 are respectively used to guide sheet 55 into the fusing station 45.

The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

Iclaim:

l. Electrographic apparatus having improved construction for facilitating the pick off of copy sheets, said apparatus comprising:

a. a support member movable along a continuous image forming path past a plurality of electrographic processing stations and in cluding on the outer surface thereof an electrographlc imaging surface having a leading edge and means defining a recess below said imaging surface at a location adjacent said leading edge;

b. means for feeding copy sheets from a supply into image transfer contact with said imaging surface in a predetermined positional relationship with respect to said leading edge such that a leading portion of a fed copy sheet extends above said recess;

. a copy sheet pickoff member mounted at a pickoff location along the image forming path of said apparatus and being movable between a first position below said imaging surface and a second position above said imaging sur face;

d. means for moving said support member around said image forming path; and

e. means for moving said pickoff member between said first and second positions in a timed relation with the movement of said support member such that the pickoff member is in said recess and below said imaging surface upon arrival of the leading portion of a positioned copy sheet at said pickoff location and is withdrawn from said recess and moved toward said second position prior to the arrival of said leading edge of said imaging surface at said pickoff location.

2. The invention defined in claim 1 further including separating means, located proximate said pickoff member in said second position, for urging away from said pickoff member the leading portion of a copy sheet separated from said imaging surface.

3. The invention defined in claim 2 wherein said separating means includes vacuum means positioned to urge the leading portion of the copy sheet away from said pickoff member.

4. The invention defined in claim 2 wherein said separating means includes corona means for urging the leading portion of the copy sheet away from said pickoff member.

5. The invention defined in claim 2 wherein said separating means includes mohair brush means positioned to urge the leading portion of the copy sheet away from said pickoff member.

6. The invention defined in claim 2 wherein said separating means includes positive air pressure means positioned to urge the leading portion of the copy sheet away from said pickoff member. 

1. Electrographic apparatus having improved construction for facilitating the pick off of copy sheets, said apparatus comprising: a. a support member movable along a continuous image forming path past a plurality of electrographic processing stations and including on the outer surface thereof an electrographic imaging surface having a leading edge and means defining a recess below said imaging surface at a location adjacent said leading edge; b. means for feeding copy sheets from a supply into image transfer contact with said imaging surface in a predetermined positional relationship with respect to said leading edge such that a leading portion of a fed copy sheet extends above said recess; c. a copy sheet pickoff member mounted at a pickoff location along the image forming path of said apparatus and being movable between a first position below said imaging surface and a second position above said imaging surface; d. means for moving said support member around said image forming path; and e. means for moving said pickoff member between said first and second positions in a timed relation with the movement of said support member such that the pickoff member is in said recess and below said imaging surface upon arrival of the leading portion of a positioned copy sheet at said pickoff location and is withdrawn from said recess and moved toward said second position prior to the arrival of said leading edge of said imaging surface at said pickoff location.
 2. The invention defined in claim 1 further including separating means, located proximate said pickoff member in said second position, for urging away from said pickoff member the leading portion of a copy sheet separated from said imaging surface.
 3. The invention defined in claim 2 wherein said separating means includes vacuum means positioned to urge the leading portion of the copy sheet away from said pickoff member.
 4. The invention defined in claim 2 wherein said separating means includes corona means for urging the leading portion of the copy sheet away from said pickoff member.
 5. The invention defined in claim 2 wherein said separating means includes mohair brush means positioned to urge the leading portion of the copy sheet away from said pickOff member.
 6. The invention defined in claim 2 wherein said separating means includes positive air pressure means positioned to urge the leading portion of the copy sheet away from said pickoff member. 